Water Parameters after removing all fish and all live rock

[gishandfish]

Curious what will happen to the water parameters of a tank if you remove all fish and live rock from a tank parameter-wise ?
So I upgraded from a 55 gallon all in one to a beautiful 90 plus sump setup. I’ve listed the 55 gallon for sale currently . I moved the lighting system , the wave maker, and about 10 lbs of sand and 60 lbs of live rock from the old all in one setup. The 55 gallon was established for over a year. I tested the water parameters almost immediately after removing the rock and fish and it was :
Nitrate:20ppm
Nitrite: .10ppm
Ammonia: 0ppm
Ph 8.1
Phos: .40 ppm
Temp:79

What parameters will change ?
The heater is still on, the sump is still running, the tiny skimmer still running but it hardly does much good since it’s so tiny in the back of the built in sump, I discovered bristleworms in the sand when I exported some sand from tank to tank.

 

[Randy Holmes-Farley]

If the nitrite is accurate, the measured nitrate will fall purely from the small amount of nitrite disappearing.

 

[gishandfish]

If the nitrite is accurate, the measured nitrate will fall purely from the small amount of nitrite disappearing.

Thank you , I ended up just draining the tank and cleaning the tank out. I put the water in a 55 gallon drum in my water closet and am aerating the water and have a heater in it so I can use it on the next partial water change for the 90 gallon. I don’t see any issues with doing that unless yall do.